Germany isn’t alone in its suffering. In March, the BBC reported that measles epidemics were also occurring in France, Italy, Poland, Romania, Switzerland, and Ukraine. No country, however, suffered more than Romania: During the first three months of 2017, it had more than 3,400 cases and 17 deaths.

Fining people to compel vaccination isn’t new. Indeed, one of the landmark cases in public health in the United States centered on whether state or local governments, acting through their police powers, had the right to do it.

In the early 1900s, a smallpox epidemic swept through Cambridge, Massachusetts. The Cambridge Board of Public Health asked all citizens to get a smallpox vaccine; those who chose not to vaccinate had to pay a $5 fine (equivalent to about $150 today). Henning Jacobson, a Lutheran minister who believed that God would reward his faithfulness and protect him, refused the vaccine and the fine. His case worked its way up to the Supreme Court, which ruled that the Cambridge Board of Health had the right to fine Jacobson for his inaction.

Arguing for the majority, Associate Justice John Marshall Harlan wrote, “The liberty secured by the Constitution of the United States does not import an absolute right to be wholly freed from restraint. There are manifold restraints to which every person is necessarily subject for the common good. Society based on the rule that each one is a law unto himself would soon be confronted with anarchy and disorder.”

Seventeen years later, in 1922, the High Court revisited its ruling in Jacobson v. Massachusetts. In the early 1920s, after refusing a smallpox vaccine, Rosalyn Zucht was expelled from Brackenridge High School in San Antonio. Like Henning Jacobson, Zucht and her case also worked their way up to the Supreme Court. But the difference was that, unlike Cambridge, San Antonio wasn’t in the midst of a smallpox epidemic. So Rosalyn’s risk of catching smallpox was negligible. Nonetheless, the Supreme Court, in a one-paragraph opinion, upheld the Jacobson ruling.

In the Jacobson and Zucht cases, the Supreme Court had ruled that citizens of the United States do not have a constitutional right to exempt themselves from vaccination or from the price levied for making that choice.

Both were also examples of mandatory vaccination, which differs from compulsory vaccination. With mandatory vaccination, people might have to pay a fine (like Henning Jacobson) or they might be prohibited from attending school (like Rosalyn Zucht) or from working in a particular hospital or business. With compulsory vaccination, on the other hand, people are vaccinated against their will or children are vaccinated against their parents will. The most recent example of compulsory vaccination occurred in Philadelphia.

The Philadelphia epidemic started when, after returning from a trip to Spain, a teenager with a blotchy rash attended a rock concert at the Spectrum concert arena. By Nov. 29, 96 schoolchildren had been stricken with the illness; a week later, it was 124; by the end of December, the number had risen to 258, and the first child had died.

The Centers for Disease Control and Prevention sent a team of scientists to determine whether the strain of measles circulating in Philadelphia was uniquely virulent. It wasn’t. Investigators soon found that the measles deaths had nothing to do with the strain of circulating virus and everything to do with the parents.

Two fundamentalist Christian churches—Faith Tabernacle Congregation and First Century Gospel Church—were at the center of the outbreak. Both were faith-healing groups, refusing vaccination as well as medical care. When their children became ill, these parents prayed instead of taking them to the hospital to receive intravenous fluids for dehydration or oxygen for pneumonia. “If I go to God and ask him to heal my body,” said church member Gordon Korn, “I can’t go to a doctor for medicine. You either trust God or you trust man.”

Public-health officials and legislators turned to the courts for help. First, they obtained a court order to examine the churches’ children in their homes, then to admit the children to a hospital for medical care. Finally, they did something that had never been done before or since: They got a court order to vaccinate children against their parents’ will. Children were briefly made wards of the state, vaccinated, then returned to their parents. At the time of the Philadelphia measles outbreak, a religious exemption to vaccination had been the law in Pennsylvania for about a decade. What the parents were doing by refusing to vaccinate their children was perfectly legal.

To prevent public-health officials from infringing on the right of faith-healing parents to exempt themselves from vaccination on religious grounds, the pastor of the Faith Tabernacle Church asked the American Civil Liberties Union to represent them. Although the ACLU has historically been willing to take on unpopular causes—like the right of neo-Nazis to march down the streets of Skokie, Illinois, in the 1970s—they refused to take the case. “There is certainly a free exercise of religion claim by the parents,” said Deborah Leavy, the executive director of the ACLU of Pennsylvania. “But there is also a competing claim that parents don’t have the right to martyr their children.”

Looking back, it’s hard to believe that the ACLU would make the choice it did. The parents of these faith-healing groups were acting within the law. But you had to be here. The city of Philadelphia was in a panic. It was a feared destination. Schools and tourists canceled trips. The Commonwealth of Pennsylvania spent hundreds of thousands of dollars creating and distributing educational pamphlets. Public-health officials, nurses, doctors, and other medical personnel were working around the clock to stem the tide of the growing epidemic. And children were dying, including those who weren’t members of faith-healing groups.

Although pushback is inevitable, the decision by German public-health officials to fine parents who leave children vulnerable to a potentially fatal infection is arguably the least they can do.